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+#lang eopl
+
+; Ben Burwell
+; Dr. Kussmaul
+; CSI-310 :: Programming Languages
+; Homework 6: Eta Conversion
+
+;; ========== PROCEDURE ==========
+;; NAME: eta-conv
+;; DESC: takes a lambda expression and returns
+;;       its eta conversion. If the expression
+;;       does not have an eta-conversion, it
+;;       returns the expression itself.
+
+(define eta-conv
+  (lambda (lst)
+    (if ;; check that the parameter is a list of length 3
+     (and
+      (list? lst)
+      (equal? (length lst) 3)
+      )
+     (if ;; it is a list with the correct length, check
+         ;; that it has an eta-conversion
+      (and
+       (equal? (car lst) 'lambda)
+       (list? (cadr lst))
+       (equal? (length (cadr lst)) 1)
+       (list? (caddr lst))
+       (equal? (length (caddr lst)) 2)
+       (equal? (caadr lst) (cadr (caddr lst)))
+       )
+      
+      ;; it does, so return the conversion
+      (car (caddr lst))
+      
+      ;; it doesn't, so return the expression
+      lst)
+     
+     ;; not a parseable expression, return it
+     lst)))
+
+;; ========== TEST CODE ==========
+;; should return a:
+(eta-conv '(lambda (x) (a x)))
+
+;; should return (lambda (x) (x a))
+(eta-conv '(lambda (x) (x a)))
+
+;; should return ()
+(eta-conv '())